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SOME lightweight bicycle wheels have a design flaw that makes them shatter
dramatically. “I had a guy come in who’d had his wheel on the kitchen table and
it exploded in his face while he was inspecting it,” says John Morgan of Bristol
University, who has been studying aluminium wheel rims. “He got aluminium in his
eyes—he was lucky not to lose his sight.”

Morgan told a meeting of the British Institute of Physics this week that the
problem happens when wheel rims are reinforced by a single aluminium section
that runs round the inside of the wheel. As brake blocks wear down the rim, he
says, cracks develop near the reinforcement and the wheel shatters. “They simply
explode—you get the whole side of the rim peeling off,” Morgan says.

LONG maligned as mere blobs, amoebas turn out to have a caring, sharing side.
By watching colonies under a microscrope, researchers in Israel have discovered
that other amoebas come to the rescue when a neighbour is struggling to divide
into two.

The “daughter” cells send out chemical distress signals when they have
difficulty severing the 3-micrometre-thick “umbilical cord” linking them to each
other. Neighbours pick up the scent and flock to the scene. “The midwife pushes
itself in between and physically wedges them apart,” says Elisha Moses, head of
the team at the Weizmann Institute in Rehovot, Israel, that made the discovery.
The team, which reports its findings in Nature (vol 41, p 430),
suspects that the “midwife” cells are attracted by a digestible sugar that
rewards them for their efforts.

BABIES breastfed for more than four months may have a higher risk of
developing hardened arteries later in life. While the researchers still advise
mothers to breastfeed, they say that the findings suggest there is an optimum
time for weaning.

Paul Leeson and Alan Lucas at the Institute for Child Health in London used
high-resolution ultrasound to measure the flexibility of artery walls in over
300 people between 20 and 28. “Longer breastfeeding was associated with stiffer
arteries,” says Leeson. One possible explanation is the higher cholesterol
content of breast milk, compared with formula milk (British Medical
Journal, vol 322, p 643). However, the study relied on people’s memories.
Independent corroboration is now needed, says Ian Booth, an expert in child
health at the University of Birmingham.

THE cracks on the surface of Venus are the hallmarks of climate change, says
Pierre Moreels at NASA’s Jet Propulsion Laboratory in Pasadena, California.

The hexagonal patterns of cracks on Venus’s surface have puzzled scientists
since 1990. Many thought lava flows had created the cracks by alternately
heating and cooling the basalt-like rock, a process that happens on Earth. But
when Moreels ran the pattern through a computer program, he found it repeats on
a scale of kilometres rather than centimetres, suggesting the cracks were caused
by huge swings in temperature.

“These cracks trace out the climate history,” he says. “It’s very different
to Earth’s.” Venus’s current surface temperature is a fiery 500 °C, but it
may have fluctuated by as much as 200 °C in the past.

CHRONIC wasting disease (CWD), a prion disease similar to BSE that affects
elk and mule deer in North America, can jump the species barrier. Elk and deer
carcasses were fed to cattle in the US until 1997. Now researchers at the
National Animal Disease Center in Ames, Iowa, have discovered that brain tissue
from deer with CWD gives cattle the disease when injected into their brains.
Feeding experiments are still in progress (Journal of Veterinary Diagnostic
Investigation, vol 13, p 91).

IF YOU give hens more control over their environment, they lay fewer eggs,
say researchers in Scotland.

One group of 30 hens could get extra food and light by pecking keys. A second
set had the same food and light as their partners but no control over when it
was delivered. Marie Haskell, formerly at the Roslin Institute near Edinburgh,
and her colleagues found that the birds who couldn’t control their living
conditions had slightly higher levels of stress hormones. But they also spent
more time preening and resting, and laid a lot more eggs. Whether they’re
happier, the researchers don’t know (Applied Animal Behaviour Science,
vol 71, p 319).